Related Party Transactions - Management Fees and Incentive Income Earned from Related Parties and Waived Fees (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Management fees
Related Party Transaction [Line Items]
Investment management revenues	$ 66,953	$ 63,623
Incentive Income
Related Party Transaction [Line Items]
Investment management revenues	9,322	53,198
Fees charged on investments held by related parties: | Management fees | Executive Managing Directors, Employees and Other Related Parties
Related Party Transaction [Line Items]
Investment management revenues	1,066	2,725
Fees charged on investments held by related parties: | Incentive Income | Executive Managing Directors, Employees and Other Related Parties
Related Party Transaction [Line Items]
Investment management revenues	$ 337	$ 1,561